This invention relates to a tubular medical instrument including as an instrument body a cuff-equipped flexible sheath, such as a sound, a catheter, a flexible tube of an endoscope and so on, which is adapted to be inserted into a body cavity (for example, a small intestine) of a human being for medical treatment.
According to a conventional method a flexible tube of such a medical instrument is inserted into a body cavity, such as a stomach, a small intestine etc., of a human being, for example, according to the peristalysis of a small intestine. This method, however, requires a longer time for insertion of the flexible tube, giving pain to the patient. Another method is to insert a flexible tube of such a medical instrument into a body cavity of human being by positively applying a push to the flexible tube. With further insertion of the flexible tube an increased resistance is encountered between the wall surface of the body cavity and the outer surface of the tube and a pushing force is not fully transmitted to the tip portion of the flexible tube. An increased pushing force imparts an increased resistance to the wall surface of the body cavity of the patient, giving a great deal of pain to the patient.
Particularly, an intestinoscope for observing a small intestine is inserted into the small intestine through a long passage consisting of the oral cavity, esophagus, stomack and duodenum. Since many bend portions are present in the long passage, a conventional intestinoscope, when inserted thereinto, imparts a relatively strong pressure to the wall of the bend portions of the passage of the human body, making it difficult to permit further insertion due to its frictional resistance and thus causing great pains to the patient. For this reason, the distance at which the intestinoscope can be inserted into the small intestine is restricted to merely 30 to 80 cm as measured from the entrance of the small intestine. For this reason, there is a demand for a medical instrument equipped with a flexible sheath adapted to be smoothly inserted up to a desired portion of a body cavity of a patient without giving any excess pain to the patient.